AR0789 on July 12, 2005

Transit of Venus on June 8, 2004

The following images were taken with my 6-inch refractor from the roof of USNO's main building, when such things were still allowed. Like many places along the East Coast, we were greeted at dawn with thick fog, and all optical surfaces immediately acquired a thick coating of dew. After a panic search of the observatory, someone located a small electric heat gun made for such things which cleared off the dew.

Spaceweather.com has a gallery of ToV photos that is worth a browse.

10 seconds before third contact

third contact

AR0618 on May 23, 2004

About my solar images…

Over time I've acquired my solar images with a cannibalized inexpensive webcam (the guts of a Philips Vesta 675), cooled with two small CPU fans, and a video camera. The cameras are attached to an inexpensive 150 mm f/8.0 achromatic refractor (one of the recent Chinese imports). The CCD in the Vesta series of webcams is a 659×494 5.6 micron square-pixel Sony color CCD. The onboard electronics resamples to produce 640×480 8-bit RGB output. The video camera CCD has 768×494 pixels, 8.4×9.8 microns.

Most of the early imaging here was done both at prime focus and with a good-quality, 3-element barlow. (Some of the oldest images were obtained with eyepiece projection.) Just in front of the camera I have an 82 Angstrom FWHM filter centered on 5200 Angstroms. This completely removes the chromatic aberration from the inexpensive doublet objective lens. Most recently, I replaced the barlow with a Televue 4x Powermate stacked with a Televue 2x "Big Barlow". These are 2-inch diameter components, so I had to cobble together a 1.25-to-2 inch adapter so I could keep using the 1.25-inch Herschel wedge. Later I obtained a 2-inch Herschel wedge from APM Telescopes in Germany.

A brief description and photos of my solar imaging setup and other hardware can be found here.

Nyquist sampling for this telescope and CCD occurs around f/24 or so. Prime focus imaging is therefore undersampled and benefits from the stacking of several frames. Flat fields, suitably normalized, were divided into all frames (thus removing most of the dust speck shadows) before any kind of processing was done. Orientations indicated are approximate. The Earth images are to scale.

Recently, special attention was paid to scattered light. I coated the insides of the refractor tube and extension tubes with the coarse, non-skid material from 3M that is used on cement steps. (It has an excellent adhesive backing.) I painted everything with Krylon ultra-flat black, including the non-skid material. Until recently, I've been using a full-aperture filter made of the excellent Baader solar filter material (both visual and photographic densities). I now use a Herschel wedge, thus dispensing with the Baader filter. The images are noticeably sharper with the wedge, and much brighter, thus allowing larger magnifications. As you'll see below, I can now easily record granulation and penumbral structures, despite the shortcomings of the inexpensive, 8-bit webcam, and the not-so-inexpensive StellaCam II video camera.

AR0606 on May 14, 2004

AR10380 and AR10377 on June 6, 2003

AR0076 on August 18, 2002

This is a small spot in its declining phase that swung into view at the eastern limb on August 12 and gradually shrank over succeeding days, finally disappearing around August 22, about three days before reaching the western limb. Notice in this image the nearly complete lack of any penumbra, as well as the grains clogging the umbrae.

AR0079 on August 18, 2002

Click on the thumbnail to see a 1/2 scale image (76 kB). For the full-resolution image (141 kB), click here instead.

AR0050 on July 29, 2002

Click on the thumbnail to see a 1/2 scale image (78 kB). For the full-resolution image (143 kB), click here instead.

AR0036 on July 21, 2002

AR0030 on July 16, 2002

This magnificent complex was easily visible with the unaided (and filtered!) eye.
Click on the thumbnail below to see a 1/2 scale image (104 kB).
For the full-resolution image (206 kB), click here instead.
For a movie clip, click here (.avi, 3.3 MB, 63 seconds, 320x240 at 10 f/s; reduced from the original 680 MB recording done at 640x480 and 5 f/s).

AR0008 and AR0016 on June 29, 2002

AR9973 on June 1, 2002

AR9934 on May 4, 2002

evolution of AR9800

AR9800 showing rapid evolution over 24 hours (January 26 and 27, 2002)
A 14-second movie of AR9800 on January 27, 2002, illustrating the effects of atmospheric seeing. Note the waves passing from left to right, due to an upper-level disturbance passing over the region.

1.7 MB .avi
2.2 MB .mpg

The AVI file is better quality than the MPG. The 10 fps video is a stretched, blurred (to remove pixel defects due to Philips driver interpolation problems), sharpened, and highly compressed copy of the original AVI captured at the telescope. Observation details are the same as for the Jan. 27 still frame shown above. Orientation of the movie is South up, West to the left.